Separation of enantiomers of non-steroidal anti-inflammatory drugs and chiral selector therefor

ABSTRACT

The invention relates to a chiral selector useful in separating underivatized enantiomers of nonsterodial anti-inflammatory agents, particularly naproxen and other arylacetic acid compounds, and relates to a process for achieving such separation utilizing the chiral selector, which is also useful in achieving the enantiomeric separation of amines, alcohol derivatives, epoxides and sulfoxides. The invention is also directed to an apparatus which comprises the chiral selectors.

This invention was made with Government support under Grant CHE-8714950awarded by the National Science Foundation. The Government has certainrights in the invention.

This is a divisional of copending application Ser. No. 847,449, filed onMar. 9, 1992, now U.S. Pat. No. 5,256,293 which is acontinuation-in-part of U.S. Ser. No. 763,043, filed on Sep. 20, 1991,now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the separation of enantiomers, i.e.,those isomers in which the arrangement of atoms or groups is such thatthe two molecules are not superimposable. The invention moreparticularly relates to a chiral selector useful, for example, as achiral stationary phase (CSP) in the liquid chromatographic separation(HPLC) of enantiomers of non-steroidal anti-inflammatory agents.

2. Description of the Prior Art

Stereoisomers are those molecules which differ from each other only intile way their atoms are oriented in space. Stereoisomers are generallyclassified as diastereomers or enantiomers; the latter embracing thosewhich are mirrorimages of each other, the former being those which arenot. The particular arrangement of atoms that characterize a particularstereoisomer is known as its optical configuration, specified by knownsequencing rules as, for example, either + or - (also D or L) and/or Ror S.

Though differing only in orientation, the practical effects ofstereoisomerism are important. For example, the biological andpharmaceutical activities of many compounds are strongly influenced bythe particular configuration involved. Indeed, many compounds are onlyof widespread utility when employed in a given stereoisomeric form.

Living organisms usually produce only one enantiomer of a pair. Thusonly (-)-2-methyl-1-butanol is formed in yeast fermentation of starches;only (+)-lactic acid is formed in the contraction of muscle; fruitjuices contain only (-)-malic acid, and only (-)-quinine is obtainedfrom the cinchona tree. In biological systems, stereochemicalspecificity is the rule rather than the exception, since the catalyticenzymes, which are so important in such systems, are optically active.For example, the sugar (+)-glucose plays an important role in animalmetabolism and is the basic raw material in the fermentation industry;however, its optical counterpart, or antipode, (-)-glucose, is neithermetabolized by animals nor fermented by yeasts. Other examples in thisregard include the mold Penicillium glaucum, which will only consume the(+)-enantiomer of an enantiomeric mixture of tartaric acid, leaving the(-)-enantiomer intact. Also, only one stereoisomer of chloromycetin isan antibiotic; and (+)-ephedrine not only does not have any drugactivity, but it interferes with the drug activity of its antipode.Finally, in the world of essences, the enantiomer (-)-carvone providesoil of spearmint with its distinctive odor, while its opticalcounterpart (+)-carvone provides the essence of caraway.

Accordingly, it is desirable and oftentimes essential to separatestereoisomers in order to obtain the useful version of a compound thatis optically active.

Separation in this regard is generally not a problem when diastereomersare involved: diastereomers have different physical properties, such asmelting points, boiling points, solubilities in a given solvent,densities, refractive indices etc. Hence, diastereomers are normallyseparated from one another by conventional methods, such as fractionaldistillation, fractional crystallization, or chromatography.

Enantiomers, on the other hand, present a special problem because theirphysical properties are identical. Thus they cannot as a rule--andespecially so when in the form of a racemic mixture--be separated byordinary methods: not by fractional distillation, because their boilingpoints are identical; not by conventional crystallization because(unless the solvent is optically active) their solubilities areidentical; not by conventional chromatography because (unless theadsorbent is optically active) they are held equally onto the adsorbent.The problem of separating enantiomers is further exacerbated by the factthat conventional synthetic techniques almost always produce a mixtureof enantiomers. When a mixture comprises equal amounts of enantiomershaving opposite optical configurations, it is called a racemate;separation of a racemate into its respective enantiomers is generallyknown as a resolution, and is a process of considerable importance.

Various techniques for separating enantiomers are known. Most, however,are directed to small, analytical quantities, meaning that otherdrawbacks aside, when applied to preparative scale amounts (themilligram to kilogram range) a loss of resolution occurs. Handseparation, the oldest method of resolution, is not only impractical butcan almost never be used since racemates seldom form mixtures ofcrystals recognizable as mirror images.

Another method, known as indirect separation, involves the conversion ofa mixture of enantiomers--the racemate--into a mixture of diastereomers.The conversion is accomplished by reacting the enantiomers with anoptically pure derivatizing agent. The resultant diastereomers are thenseparated from one another by taking advantage of their differentphysical properties. Once separated by, for example, fractionalcrystallization, or more commonly, chromatography, the diastereomers arere-converted back into the corresponding enantiomers, which are nowoptically pure. Though achieving the requisite separation, the indirectmethod suffers in that it is time consuming and can require largequantities of optically pure derivatizing agent which can be expensiveand is oftentimes not recoverable. Moreover, the de-derivatizing stepmay itself result in racemization thus defeating the purpose of theseparation earlier achieved.

A more current method that avoids some of the drawbacks attendant theindirect method is known as the direct method of separation. The directmethod, much like the indirect method, involves the formation of adiastereomeric species. However, unlike the indirect method, thisspecies is transient, with the stability of one species differing fromthe other.

In one application of the direct method, the mixture of enantiomers isallowed to interact with a chiral stationary phase which, for example,could reside in a chromatographic column. The enantiomer that interactsmore strongly with the chiral stationary phase will have a longerresidence time, hence a separation of enantiomers will occur. When themode of interaction with the chiral stationary phase can becharacterized, the elution order can be predicted. Examples of chiralstationary phases include those based upon(L)-N-(3,5-dinitrobenzoyl)leucine, which is useful in separatingenantiomers of N-aryl derivatized amino acids and esters, and thosebased upon (L)-N-(1-naphthyl)leucine which has been used to effectivelyseparate N-(3,5-dinitrobenzoyl) derivatized amino compounds. HPLCcolumns packed with silica-bonded CSP's of a variety of pi-electronacceptors and pi-electron donors--including derivatives ofphenylglycine, leucine, naphthylalanine and naphthylleucine arecommercially available from Regis Chemical Company, Morton Grove, Ill.

In another application of the direct method, disclosed in copending andcommonly assigned patent application Ser. No. 528,007, filed May 23,1990, now U.S. Pat. No. 5,080,795, enantiomers of such compounds asamino acids, amino esters, alcohols, amines, sulfonic acids orderivatives thereof are separated by means of a liquid membranecontaining a chiral carrier, such as the derivatized amino acid(S)-N-(1-naphthyl)leucine octadecyl ester. The chiral carrier is capableof forming a stable complex with one of the enantiomers. The liquidmembrane is located on one side of a semi-permeable barrier, and themixture of enantiomers is located on the other side of the barrier. Theliquid membrane containing the chiral carrier impregnates thesemi-permeable barrier under conditions effective to permit or cause astable complex between the chiral carrier and one of the enantiomers toform in the barrier. The liquid membrane containing the stable complexis passed to a second location where the conditions are effective todissociate the stable complex, allowing the recovery of thecomplex-forming enantiomer to take place. In one embodiment of thisapplication, a hollow fiber membrane is employed as the semi-permeablebarrier.

It is widely recognized that stereoisomers of pharmaceutical agents mayhave drastically different pharmacological potencies or actions. Amongthose pharmaceutical agents known to elicit differing physiologicalresponses depending on the optical configuration used are theanti-phlogistics, which are those drugs used to counteract inflammation.Antiphlogistics are generally divided into two classes: nonsteroidalanti-inflammatory agents (NSAIAs), which are generally employed in thesymptomatic treatment of inflammation, such as occurs with arthritis,and antirheumatics, which act in a more therapeutic fashion.

While NSAIAs can have vastly different chemical structures, most arearyl acidic molecules (though the acidic function is not essential foranti-inflammatory activity) or metabolic precursors thereof, oftenpossessing two to three aromatic or heteroaromatic rings, either fusedor linear and which are often nonplanar; the presence of a halogen orisostere atom or group usually enhances activity. Nonsteroidalanti-inflammatory agents are generally categorized into the followinggroups: 1) salicylates, which are derivatives of salicylic acid andinclude agents such as aspirin; 2) 5-pyrazolone derivatives, most ofwhich are 3,5-pyrazolidinedione derivatives and include agents such asphenylbutazone; 3) fenamates and isosteres, which are eithern-arylanthranilic or 2-aminonicotinic acid derivatives, which includesuch agents as meclofenmate sodium; 4) oxicams, which are mostlyN-heterocyclic carboxamides of 4-hydroxy-2H-1,2-benzothiazine1,1-dioxide, and include such agents as piroxicam; 5) other acidiccompounds, such as aminobenzoic acid salts (e.g. aminobenzoatepotassium), pyrocathecol derivatives (e.g. nepitrin) and thesulfonanilide derivative, nimesulide; and 6) nonacidic heterocycliccompounds, such as indazole derivatives.

The more commonly employed NSAIAs, however, are those in the categoryknown as arylacetic acid compounds. Most arylacetic acid compounds sharecertain structural features: a carboxyl group or its equivalent, such asenolic acid, hydroxamic acid, sulfonamide, or a tetrazole moiety,separated by one carbon atom from a planar aromatic nucleus (hencemaking them acidic molecules). To the flat aromatic nucleus, one or morelarge lipophilic groups may be attached. The presence of an α-methylsubstituent normally enhances potency, while an increase in size of thisα-substituent usually diminishes activity.

Generally, the category known as arylacetic acid compounds is subdividedinto the following subgroups: phenylacetic acid compounds, such asdiclofenac sodium; phenylpropionic acid compounds, such as ibuprofen andnaproxen; phenylbutyric acid compounds, such as indobufen;aryloxyalkanoic acid compounds, such as furobufen; and heteroarylaceticacid compounds, such as etodolac.

Given the importance of nonsteroidal anti-inflammatory agents,arylacetic acid compounds in particular, and of the criticality ofemploying the proper enantiomeric form, much effort has been madeinvestigating methods for obtaining the desired optical configuration ofthese compounds. These techniques have ranged from attempts atsynthesizing one of the two optical isomers in pure form in the firstinstance, to tailoring the more traditional methods of enantiomerseparation to meet this particular need.

While asymnetric synthesis would theoretically reduce or eliminate theneed for complex stereospecific separations, these synthetic techniqueshave met with limited commercial success in general applications, andhave had even less success with respect to nonsteroidalanti-inflammatory agents. Stereochemical isolation and purification ofthese compounds have thus far relied upon chromatographic separationtechniques.

Of the separation techniques in this regard, most have requiredderivatization of the particular NSAIA involved with some techniqueseven employing a chiral derivatizing agent so as to form diastereomers.However, these derivatization-dependent methods introduce increased timeand cost factors into the separation and, even more importantly,introduce the possibility of error into the separation process, whichnow requires further steps and reactions to achieve resolution, whichitself may prove to be ultimately less effective.

Procedures which require derivatization of NSAIAs with chiral reagentsin order to obtain diastereomers are particularly problem prone, giventhat the rate of reaction of the chiral reagent with individualenantiomers may be different thus leading to a ratio of diastereomerswhich does not reflect the initial ratio of analyte enantiomers.Further, these procedures require scrupulous maintenance of theenantiomeric purity of the chiral reagent and avoidance of partialracemization of the analyte and chiral reagent during the course of thederivatization procedure. Lastly, the diastereomeric product ultimatelyobtained may give non-identical detection results, thus requiringadditional validation steps.

Accordingly, to avoid these drawbacks, efforts have been made to obtaindirect chromatographic separation of underivatized NSAIA enantiomers.However, these efforts have failed to be generally applicable to theentire class of NSAIAs, and have failed to be even generally applicableto any category of NSAIAs, such as the arylacetic acid category, whichincludes naproxen and other profen-type agents. For example, Hermanssonand Eriksson in "Direct Liquid Chromatographic Resolution of AcidicDrugs Using Chiral α-1-Acid Glycoprotein Column (Enantiopac®), J. Liq.Chromatogr., 9, 621 (1986) report a chromatographic separation factor(α) of greater than 4 for underivatized naproxen using an α-1-acidglycoprotein chiral stationary phase and an achiral ion pairing reagent.However, the separation of enantiomers using a protein-derivedstationary phase suffers from several important drawbacks which makethese methods less than desirable for practical applications: First,since proteins are only available in one enantiomeric form, or antipode,elution orders cannot be reversed, which is often desirable in theanalytical determination of enantiomeric purity. And, in any event, if achiral selector is to find practical application as an enantioselectivemembrane transport agent, it is desirable that it be available in bothenantiomeric forms. Secondly, proteins and protein-derived chiralstationary phases typically have rather low stability compared tosynthetic chiral selectors, thus the lifetime of a protein selector or achiral stationary phase derived therefrom, will not be as great as thatfor a synthetic selector; this is especially true where elevatedtemperatures, extremes of pH or organic solvents are involved. Finally,owing to the extremely low concentration of binding sites on theprotein, preparative scale resolutions are not feasible.

Other efforts in this regard include that reported by Petterson andGioeli in "Improved Resolution of Enantiomers of Naproxen by theSimultaneous Use of a Chiral Stationary Phase and a Chiral Additive inthe Mobile Phase", J. Chromatogr., 435, 225 (1988) in whichunderivatized enantiomers of naproxen were separated on aquinidine-based chiral stationary phase using quinine as a mobile phaseadditive. Separation, however, was marginal, with α=1.18, and poor bandshape was exhibited, hence making this technique impractical forpreparative purposes.

Thus there continues to be a pressing need for a process of separatingenantiomers of NSAIAs, especially those categorized as arylacetic acidcompounds, which does not require derivatization and which is notprotein-based and which can provide a high degree of resolution and isgenerally applicable at least across an entire category of NSAIAs.

SUMMARY OF THE INVENTION

The present invention overcomes the inadequacies attendant enantiomericseparation techniques known heretofore for nonsteroidalanti-inflammatory agents. The present invention is directed to a chiralselector which can enantioselectively complex with underivatizednonsteroidal anti-inflammatory agents, particularly those classified asarylacetic acid compounds and hence provide a process for the efficientseparation of the enantiomers of these compounds.

The chiral selector of the present invention is a compound having theformula ##STR1## wherein R₁ is ##STR2## R₂ is O, S or NH; R₃ and R₄ areeach independently hydrogen or lower alkyl;

R₅ is hydrogen or CH═CH₂ ;

R₆ and R₇ are each independently hydrogen or lower alkyl or R₆ and R₇are attached to form a 6 member aromatic ring;

X is O, S, NH or CH;

X₁ is O, S, NH or CH;

m is 0 or 1;

n is 0 or 1;

R₈ and R₉ are each independently NO₂, N(R₁₀)₃ ⁺ CN, COOR₁₁, SO₃ H orCOR₁₂, wherein R₁₀, R₁₁ and R₁₂ are each independently hydrogen or loweralkyl; and

o is 0 or an integer from 1 to 12, said compound being an R or an Senantiomer or a mixture of R and S enantiomers.

In one embodiment of the subject invention, the chiral selector isemployed in a process of separating enantiomers of a nonsteroidalanti-inflammatory agent having a first and second optical configuration,wherein said nonsteroidal anti-inflammatory agent has the formula##STR3## wherein R₁₃ is aryl or a nitrogen, sulfur or oxygen containingheterocyclic moiety either of which may be unsubstituted or substitutedwith lower alkyl, lower alkoxy, aryl, aryloxy, aroyl, alkanoyl orhalogen, and

R₁₄ and R₁₅ are each independently hydrogen or lower alkyl,

with a chiral selector having the formula described hereinbefore, saidchiral selector being an R or S enantiomer under conditions effective toform a complex between an enantiomer of said non-steroidalanti-inflammatory agent having said first optical configuration and anenantiomer of said chiral selector; and

recovering the non-complexed enantiomer of said non-steroidalanti-inflammatory agent having said second optical configuration.

In another embodiment of the present invention, the chiral selector isemployed in a process of separating enantiomers of various amines,alcohol-derivatives, sulfoxides and epoxides, respectively.

The present invention is also directed to an apparatus utilizing thechiral selector. Apparatuses in this regard include liquidchromatographic columns, enantioselective membrane transport devices andliquid-liquid partitioning devices, such as countercurrentchromatographic devices.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in one embodiment to a process for theenantiomeric separation of nonsteroidal anti-inflammatory agents,particularly those agents categorized generally as arylacetic acidcompounds and more particularly those groups known as phenylpropionicacid compounds and heteroarylacetic acid compounds. The presentinvention further relates to a chiral selector compound having a certainstructure, the use of which achieves the enantiomeric separation.Significantly, in the practice of the invention, no derivatization ofthe enantiomers is required prior to effecting separation, althoughderivatization may be employed without detriment.

The process of the invention has especial utility in separatingenantiomers of underivatized arylacetic acid compounds. This class ofnonsteroidal anti-inflammatory agents may be identified by the generalformula: R1 ? ##STR4## wherein R₁₃ is an aryl or a nitrogen, sulfur oroxygen containing heterocyclic moiety, either of which may beunsubstituted or substituted with lower alkyl, lower alkoxy, aryl,alkoxyaryl, aralkyl, aryloxy, aroyl, alkanoyl, aralkanoyl or halogen,and

R₁₄ and R₁₅ are each independently hydrogen or lower alkyl.

These compounds are of the R of S optical configuration and whenprepared are normally produced in racemic form, thus making enantiomericseparation a necessity for practical purposes.

Among the preferred arylacetic acid compounds which may beenantiomerically separated by the process of the present invention arethose generally in the subgroup known as phenylpropionic acid compoundsand heteroarylacetic acid compounds.

Representative compounds of the phenylpropionic acid subgroup include:alminoprofen, benoxaprofen, carprofen, cicloprofen, cinaproxen,cliprofen, dexindoprofen, esflurbiprofen, fenclorac, fenoprofen,fenoprofen calcium, flunoxaprofen, fluprofen, flurbiprofen, frabuprofen,furaprofen, furcloprofen, hexaprofen, ibufenac, ibuprofen, ibuprofenaluminun, ibuproxam, indoprofen, isoprofen, ketoprofen, lisiprofen,lobuprofen, loxoprofen, mexoprofen, miroprofen, naproxen, naproxensodium, naproxol, piketoprofen, pimaprofen, pineprofen, pirprofen,pranoprofen, protizinic acid, rosmarinic acid, suprofen, tazeprofen,tetriprofen, ximoprofen and zoliprofen.

Representative compounds of heteroarylacetic acid subgroup include:acemetacin, anirolac, bensuldazic acid, bufezolac, cinmetacin, clidanac,clometacin, clopirac, delmetacin, duometacin, eltenac, etodolac,fenclozic acid, fentiazac, glucametacin, indomethacin, indomethacinsodium trihydrate, isofezoluc, ketorolac, lonazolac, calcium niometacin,orpanoxin, oxametacin, oxaprozin, pimetacin, pirazolac, prodolic acid,proglumetacin, sermetacin, sulindac, talmetacin, tianafac, tiaprofenicacid, tioxaprofen, tolmetin, tolmetin sodium, zidometacin and zomepiracsodium.

The structures of the more preferred compounds of these groups to whichthe present process has particular utility are given, in Table 1, below:

                                      TABLE 1                                     __________________________________________________________________________     ##STR5##                                                                                               ##STR6##                                            Naproxen                 Ibuprofen                                             ##STR7##                                                                                               ##STR8##                                            Ketoprofen               Pirprofen                                             ##STR9##                                                                                               ##STR10##                                           Carprofen                Fenoprofen                                            ##STR11##                                                                                              ##STR12##                                           Flurbiprofen             Cicloprofen                                           ##STR13##                                                                                              ##STR14##                                           Tiaprofenic Acid         Etodolac                                             __________________________________________________________________________

The present process is most utile in performing enantiomeric separationon naproxen.

The substituents in the formulas related herein are described asfollows:

As employed herein, the lower alkyl groups, singly or in combinationwith other groups, contain up to 6 carbon atoms which may be in thenormal or branched configuration, including methyl, ethyl, propyl,isopropyl, butyl, isobutyl, t-butyl, amyl, pentyl, hexyl and the like.The preferred alkyl groups contain 1 to 3 carbon atoms.

The aryl groups are aromatic rings containing from 6 to 14 carbon atoms.Examples of aryl groups include phenyl, α-naphthyl and β-naphthyl.

The alkoxyaryl groups, singly or in combination with other groups,contain lip to 16 carbon atoms, with each alkoxy group containing up to6 carbon atoms which may be in the normal or branched configuration, andeach aryl group containing from 4 to 10 carbon atoms. Preferably, eachalkoxy group contains to 1 to 3 carbon atoms, and each aryl groupcontains 4 to 6 carbon atoms.

The aralkyl groups, singly or in combination with other groups, containup to 16 carbon atoms with each aryl group containing from 6 to 10carbon atoms and each alkyl group containing up to 6 carbon atoms whichmay be in the normal or branched configuration. Preferably, each arylgroup contains 6 carbon atoms and each alkyl group contains 1 to 3carbon atoms.

The aryloxy groups, singly or in combination with other groups containfrom 6 to 10 carbon atoms. Preferably, each aryl group contains 6 carbonatoms.

The aroyl groups, singly or in combination with other groups, containfrom 7 to 11 carbon atoms. Preferably, the aryl group contains 6 carbonatoms.

The alkanoyl groups, singly or in combination with other groups, containup to 7 carbon atoms. Preferably, the alkyl groups contain 1 to 3 carbonatoms.

The aralkanoyl groups, singly or in combination with other groups,contain up to 17 carbon atoms, with each aryl group containing from 6 to10 carbon atoms and each alkyl group containing up to 6 carbon atoms.Preferably, each aryl group contains 6 carbon atoms and each alkyl groupcontains 1 to 3 carbon atoms.

The lower alkoxy groups, singly or in combination with other groups,contain up to 6 carbon atoms which may be in the normal or branchedconfiguration. Preferably each alkyl group contains 1 to 3 carbon atoms.

The alkaryl groups, singly or in combination with other groups, containup to 16 carbon atoms with each alkyl group containing up to 6 carbonatoms which may be in the normal or branched configuration, and eacharyl group containing from 6 to 10 carbon atoms. Preferably, each alkylgroup contains 6 carbon atoms. The aralkenyl groups, singly or incombination with other groups, contain up to 30 carbon atoms, with eacharyl group containing up to 10 carbon atoms and each alkenyl groupcontaining up to 20 carbon atoms. Preferably, each aryl group contains10 carbon atoms and each alkenyl group contains up to 15 carbon atoms.

The halogens include fluorine, chlorine, bromine and iodine. Preferredhalogens include fluorine and chlorine.

As employed herein, the expression "a nitrogen, sulfur or oxygencontaining heterocyclic moiety" is meant to include those heterocyclicring systems which include at least one sulfur, nitrogen or oxygen ringatom but which may include one or several of said atoms. The expressionalso includes saturated and unsaturated heterocyclics as well asheteroaromatic rings. These groups contain from 10 to 15 ring atoms onthe heterocyclic moiety. Representatives heterocyclics include furan,thiophene, pyrrole, pyridine, pyrazole, pyrazine, pyrimidine,pyridazine, oxazole, quinoline, isoquinoline, indole, benzothiophene,benzofuran, imidizole, benzoxazote, piperazine, tetrahydrofuran and thelike.

The chiral selector of the present invention is a compound having thefollowing formula: ##STR15## wherein R₁ is ##STR16## R₂ is O, S or NH;R₃ and R₄ are each independently hydrogen or lower alkyl;

R₅ is hydrogen or CH═CH₂ ;

R₆ and R₇ are each independently hydrogen or lower alkyl or R₆ and R₇are attached to form a 6 member aromatic ring;

X is O, S, NH or CH;

X₁ is O, S, NH or CH;

m is 0or 1;

n is 0 or 1;

R₈ and R₉ are each independently NO₂, N(R₁₀)₃ ⁺, CN, COOR₁₁, SO₃ H orCOR₂, wherein R₁₀, R₁₁ and R₁₂ are each independently hydrogen or loweralkyl; and

o is 0 or an integer from 1 to 12, said compound being an R or an Senantiomer or a mixture of R and S enantiomers.

In the practice of the present invention, the substituents denoted aboveas ##STR17## may be in the trans, or the cis position relative to oneanother; the cis position is preferred.

In preferred embodiments of the chiral selector of the instant invention

R₁ is preferably R₈ ##STR18## R₂ is preferably NH. R₃ and R₄ arepreferably each independently hydrogen or methyl, with hydrogen beingmore preferred.

R₅ is preferably CH═CH₂.

R₆ and R₇ are preferably attached to form a 6 member aromatic ring whenX is O, S or NH, preferably O, and m is 1 and n is 0, or R₆ and R₇ arepreferably attached to form a 6 member aromatic ring when X₁ is O, S orNH, preferably O, and m is 0 and n is 1. In a more preferred embodiment,R₆ and R₇ are hydrogen or methyl, methyl being more preferred, and X andX₁ are each CH and m and n are each 1.

R₈ and R₉ are preferably NO₂.

A particularly preferred chiral selector for effecting separation ofnonsteroidal anti-inflammatory agents, particularly those classified asarylacetic acid compounds and more particularly, those in the subgroupknown as phenylpropionic acid compounds and heteroarylacetic acidcompounds, is the chiral selector having the formula ##STR19##hereinafter identified as CS-10 and also known by its name4-(3,5-dinitrobenzoyl)amino-3-(undec-10-enyl)-1,2,3,4-tetrahydrophenanthrene.

Another preferred chiral selector for effecting separation ofnon-steroidal anti-inflammatory agents, particularly those classified asarylacetic acid compounds and more particularly, those in the subgroupknown as phenylpropionic acid compound and heteroarylacetic acidcompound is the chiral selector having the formula: ##STR20##hereinafter identified as CS-2 and also known by its name4-oxo-3-allyl-1,2,3,4-tetrahydrophenanthrene.

Still another preferred chiral selector for effecting separation ofnon-steroidal anti-inflammatory agents, particularly those classified asarylacetic acid compounds and more particularly those in the subgroupknown as phenyl propionic acid compound and heteroarylacetic acidcompounds is the chiral selector having the formula: ##STR21##hereinafter identified as CS-8 and also known by its name6,7-Dimethyl-4-[N-(3,5-dinitrobenzoyl)]amino-3-(10-undecenyl)-1,2,3,4-tetrahydrophenanthrene.

In another embodiment of the present invention, the chiral selectorhaving the formula described hereinabove is employed in a process forthe separation of enantiomers of amines having the general formula##STR22## wherein R₁₆ and R₁₇ are each independently hydrogen, aralkyl,aralkenyl or R₁₆ and R₁₇ together with the N to which they are attachedform a 3, 4, 5 or 6 member ring having the general formula ##STR23##wherein R₂₁ and R₂₂ are each independently hydrogen, lower alkyl, aryl,alkaryl or aralkyl and q is 1, 2, 3 or 4, R₁₈ is C or S, R₁₉ is loweralkyl, aryl, alkaryl or aralkyl any of which may be unsubstituted orsubstituted with NO₂, N(R₂₃)₃ ⁺, CN, COOR₂₄, SO₃ H or COR₂₅ wherein R₂₃,R₂₄ and R₂₅ are each independently hydrogen or lower alkyl, R₂₀ is O andp is 1 when R₁₈ is S, and p is 0 when R₁₈ is C.

Representative amines having this formula are shown in Table 2, below:

                                      TABLE 2                                     __________________________________________________________________________     ##STR24##                                                                                             ##STR25##                                                                                           ##STR26##                       ##STR27##                                                                                             ##STR28##                                                                                           ##STR29##                      __________________________________________________________________________

In yet another embodiment of the present invention, the chiral selectorhaving the formula described hereinabove is employed in a process forthe separation of enantiomers of alcohol derivatives having the generalformula ##STR30## wherein R₂₆ is hydrogen, lower alkyl or aryl either ofwhich may be unsubstituted or substituted with NO₂, N(R₂₉)₃ ⁺, CNCOOR₃₀, SO₃ H or COR₃₁ wherein R₂₉, R₃₀ and R₃₁ are each independentlyhydrogen or lower alkyl, R₂₇ is NR₃₂ wherein R₃₂ is hydrogen or loweralkyl, R₂₈ is lower alkyl, aryl or aralkyl and r is 0 or 1.

Representative alcohol derivatives having this formula are shown inTable 3, below:

                                      TABLE 3                                     __________________________________________________________________________     ##STR31##                                                                                     ##STR32##                                                                                     ##STR33##                                    __________________________________________________________________________

In still another embodiment of the present invention, the chiralselector having the formula described hereinabove is employed in aprocess for the separation of enantiomers of epoxides having the generalformula ##STR34## wherein R₃₃, R₃₄, R₃₅ and R₃₆ are each independentlyhydrogen, lower alkyl, aryl, alkaryl or aralkyl.

Representative epoxides having this formula are shown in Table 4, below

                  TABLE 4                                                         ______________________________________                                         ##STR35##                                                                    ______________________________________                                    

In yet still another embodiment of the present invention, the chiralselector having the formula described hereinabove is employed in aprocess for the separation of enantiomers of sulfoxides having thegeneral formula ##STR36## wherein R₃₇ and R₃₈ are each independentlylower alkyl or an aryl or a nitrogen, sulfur or oxygen containingheterocyclic moiety, or R₃₇ or R₃₈ may together with the S to which theyare attached from a 4 or 5 member ring having the formula ##STR37##wherein R₃₉ is hydrogen or lower alkyl, R₄₀ is O or S, R₄₁ is aryl and sis 1 or 2.

Representative sulfoxides having this formula are shown in Table 5,below

                  TABLE 5                                                         ______________________________________                                         ##STR38##                                                                    ______________________________________                                    

The chiral selectors of the present invention may be prepared byconventional chemical preparation techniques. For illustrative purposes,the preparation of the preferred chiral selector is described below butthose skilled in the art can readily appreciate the modificationsnecessary to prepare other chiral selectors within the scope of theformula depicted hereinabove.

The synthetic sequence used to prepare the chiral selector of thepresent invention is exemplified for CS-10, as shown in Table 7, below.Those of skill in the art will appreciate that the synthetic sequencedelineated hereinbelow is readily modified to provide other chiralselectors of the instant invention.

                                      TABLE 7                                     __________________________________________________________________________     ##STR39##                                                                     ##STR40##                                                                    __________________________________________________________________________

This preparation began with 4-oxo-1,2,3,4-tetrahydrophenanthrene(identified as Compound A, Table 7), as described by Scroeter, G. et al.in "Uber die Hydrierung des Phenanthrens, Ber. der. Deutschen Chem, 62,645, 1929. Alkylation of this phenanthrene with 11-iodoundec-1-ene wasperformed in refluxing benzene using potassium t-butoxide as a base.Reductive alkylation of the resulting monoalkylated ketone (identifiedas Compound B, Table 7), using sodium cyanoborohydride and ammoniumacetate in isopropyl alcohol at 95° C. gave a mixture of cis- andtrans-amines (identified as Compound C, Table 7), which were convertedto the corresponding 3,5-dinitrobenzamides (identified as CS-10, Table7), without purification. The mixture of cis- and trans-amides (about5:1) was then separated by flash chromatography upon silica gel.Enantiomeric separation was performed at this stage using a preparativeversion of a chiral stationary phase described by Pirkle, Deming andBurke in Chirality, 3:183-187 (1991) the contents of which areincorporated herein by reference; this chiral stationary phase wasderived from S-N-(1-naphthyl) leucine and having the formula ##STR41##

Enantiomeric separation by means of the chiral selectors of theinvention may be achieved in a variety of techniques known in the art.In one embodiment, the chiral selector may form the active portion ofthe stationary phase in an HPLC column. In this embodiment of thepresent invention, the terminal W of the formula must be CH═CH₂ so as topermit the chiral selector to be immobilized on a support which issuitable for use in chromatographic separations. Supports in this regardinclude, e.g., silica and alumina. In one configuration, the chiralselector is immobilized by covalently bonding it to silanized silica.Thus, for example as shown in Table 8, below, hydrosilation ofenantiomerically pure CS-10 gives a silane (identified as Compound D,Table 8) which was bonded to 5μ (100 Å silica gel and slurry packed intoa stainless steel analytical HPLC column (4.6 mm×250 mm) to give achiral stationary phase based on CS-10 (CSP-10)).

                  TABLE 8                                                         ______________________________________                                         ##STR42##                                                                     ##STR43##                                                                     ##STR44##                                                                    ______________________________________                                    

Since the chiral selectors of the invention are optically active, it isnecessary to separate the chiral selectors so that either the R or the Senantiomer of the chiral selector is employed as the stationary phase inthe column, depending upon which of the enantiomers to be separated isto be preferentially bound to the chiral selector.

The techniques of enantiomer separation by HPLC are known in the art.Commercially available HPLC columns employing chiral stationary phases,such as those available from Regis Chemical Company, can be employed inpracticing the subject invention. See, for example, "Systematic Studiesof Chiral Recognition Mechanisms", W. H. Pirkle, et al., Pages 23-25 in"Chiral Separations", Stephenson and Wilson, eds. Plenum Press, NewYork, 1988, the contents of which are incorporated herein by reference.

In another embodiment of the present invention, the chiral selectors ofthe subject invention may be employed to effect separations usingsemi-permeable membranes wherein the chiral selector forms part of amobile phase. Such techniques are also well known, including the use ofsemi-permeable membranes in the form of hollow fiber membranes. In thisembodiment, it is preferred that the terminal W in the formula of thechiral selector be hydrogen so as to minimize covalent bonding by thechiral selector. In one particularly useful embodiment, the chiralselector forms part of a liquid membrane passing on one side of asemi-permeable barrier with enantiomers to be separated passing on theother side of the barrier. The pores of the membrane become impregnatedwith the liquid membrane containing the chiral selector. One of theenantiomers forms a complex with the chiral selector, passes through themembrane into the moving liquid membrane and is conducted to a secondlocation wherein disassociation takes place. This technique is disclosedin commonly assigned patent application Ser. No. 528,007, filed May 23,1990, now U.S. Pat. No. 5,080,795, the contents of which areincorporated herein by reference.

The following examples are given to illustrate the scope of theinvention. Because these examples are given for illustrative purposesonly, the invention embodied therein should not be limited thereto.

EXAMPLE 1 Preparation of CS-10 Apparatus and Materials

Chromatographic analysis was performed using a Rainin HPX Rabbit pump, aRheodyne Model 7125 injector with a 20 μl sample loop, a Milton Roy-LDCUV absorbance Monitor D® fixed wavelength detector operating at 254 nm,and a Shimadzu CR1A integrating recorder.

Solvents used were HPLC grade or were distilled prior to use.(S)-naproxen was used as received from Sepracorp. Dimethylchlorosilanewas obtained from Petrarch Chemicals.

Preparation of4-(3,5-dinitrobenzoyl)amino-3-(undec-10-enyl)-1,2,3,4-tetrahydrophenanthrene(CS-10) (see Table 7, supra)

Synthesis of 11-Iodoundec-1-ene

A solution of 93.5 g of undec-10-en-1-ol and 100 mL of triethylamine in500 mL of dry dichloromethane was treated with 68.7 g of methanesulfonylchloride at 0° C. according to the method reported by Crossland, R. K.,et al. in "A Facile synthesis of Methanesulfonate Esters" J. Org. Chem.,35, 3195 (1970). The crude reaction mixture was then evaporated andpartitioned between water and ether. The ether layer was collected,washed with water, then dried over anhydrous magnesium sulfate.Filtration and evaporation gave 142 g of a colorless oil which wasimmediately converted to the iodo compound. A solution of 137 g sodiumiodide and 1.2 g dicyclohexano-18-crown-6 in 150 mL of water was stirredwith 64 g of the crude mesylate On a steam bath for 5 h. The reactionmixture was then extracted several times with ether, the combined etherfractions were washed with water, then dried over anhydrous magnesiumsulfate. Filtration and evaporation gave the crude iodo compound as anoil which was vacuum distilled to give 62.8 g (90% yield) of almostcolorless oil, b.p. 118°-122° C./4.5 mn Hg, lit. 104° C./2 mm Hg. Thiscompound was used in the synthesis of the alkylated ketone or describedhereinbelow.

Synthesis of the alkylated ketone (Compound B, Table 7)

In a 1L three-necked round bottom flask equipped with a Teflon paddlestirrer, nitrogen inlet, and a Dean-Stark trap, 500 mL of benzene wasdried by azeotropic water removal. Solid potassium tert.-butoxide, 12.3g, was added at 50° C. giving a clear solution. A solution of 8.9 g of4-oxo-1,2,3,4-tetrahydrophenanthrene, as described by Scroeter, G. etal. in "Uber die Hydrierung des Phenanthrens", Ber. der Deutschen Chem.,62, 645 (1929) (Compound A, Table 7) and 14 g of 11-iodoundec-1-ene(synthesized according to the method described above) in 100 mL of drybenzene was added at 40° C., causing the reaction mixture to darkensomewhat. Stirring at 40° C. was continued for 45 min., then thereaction mixture was heated at reflux for 2 h. During this period,approximately 400 mL of benzene was allowed to distill off. Cooling thereaction mixture followed by extraction with water, drying the organicphase with anhydrous magnesium sulfate, filtration, and evaporation gave19 g of a dark oil which was purified by flash chromatography on silicausing 1:1 dichloromethane/hexane as eluent to give 9.9 g of alkylatedketone (Compound B, Table 2) (63% yield).

Reductive amination to form4-amino-3-(undec-10-enyl)-1,2,3,4-tetrahydrophenanthrene (Compound C,Table 7)

In a 250 mL thick-walled Parr bottle was mixed 5 g of alkylated ketone(Compound B, Table 7) as synthesized according to the method describedabove, 6 g sodium cyanoborohydride, 30 g ammonium acetate, and 100 mL2-propanol. After securely closing the bottle with a rubber stopper, thecontents were heated to 90°-95° C. for 24 h by immersion of the bottlein a steam bath. A safety shield was placed in front of the bottle,which had also been wrapped in cloth. After cooling and evaporation thecrude product was partitioned between ether and water, the ether layerwas dried with anhydrous magnesium sulfate, filtered, and evaporated togive 5.9 g of an oil which showed no. traces of alkylated ketone(Compound B, Table 7) by thin layer chromatography (TLC). The crudeamine was carried on to the next step without further purification.

Synthesis of4-(3,5-dinitrobenzoyl)amino-3-(undec-10-enyl)-1,2,3,4-tetrahydrophenanthrene(CS-10)

The crude amine synthesized according to the method described above wasdissolved in 150 mL dichloromethane and stirred with excess saturatedsodium hydrogen carbonate solution. 3,5-Dinitrobenzoyl chloride, 5 g,dissolved in the minimum amount of dichloromethane was then added, andthe resulting two-phase mixture was stirred vigorously for 1 h. Theorganic layer was then dried, concentrated to approximately 20 mLvolume, and purified by flash chromatography on silica withdichloromethane as eluent. Both cis and trans isomers of CS-10 wereobtained in about a 5:1 ratio, respectively. Separation of thediastereomers was incomplete by flash chromatography; nevertheless,pooling of the pure fractions containing the desired cis diastereomergave 2.2 g of CS-10 (a 28% yield from Compound B, Table 7).

Separation of the enantiomers of CS-10

Separation of the enantiomers of CS-10 was performed with a chiralstationary phase derived from S-N-(1-naphthyl)leucine which was preparedas described by Pirkle, Deming and Burke in Chirality, 3:183-187 (1991)the contents of which are incorporated herein by reference.

Separation of the enantiomers of CS-10 was performed using this chiralstationary phase derived from S-N-(1-naphthyl)leucine at a flow rate of40 mL/min of 10% 2-propanol in hexane with continuous redistillation andrecycling of mobile phase. Two bands were obtained. 1 g samples of thenearly pure fast-eluting enantiomer of CS-10 having the (R,R)configuration were isolated, as were samples of the slow-elutingenantiomer of CS-10 having the (S,S) configuration.

Chiral Stationary Phase of CS-10 Hydrosilation of CS-10

The fast eluting enantiomer (R,R) of CS-10 was dissolved, 1 g, in amixture of 10 mL of dimethylchlorosilane (Petrarch Chemicals) and 10 mLof dichloromethane. Chloroplatinic acid (about 10 mg), dissolved in aminimum amount of 2-propanol, was then added, and the reaction mixturewas heated at reflux under a nitrogen atmosphere. After 2 h, a quenched(as described below) aliquot of the reaction mixture was subjected toTLC analysis, showing the disappearance of starting material. Thereaction mixture was evaporated to dryness on a rotary evaporator togive the crude chlorosilane as a dark oil. Residual dimethylchlorosilanewas removed by three successive additions and evaporations of smallportions of dichloromethane. A solution of 5 mL triethylamine, 5 mLabsolute ethanol, and 5 mL diethyl ether was then added to the crudechlorosilane and the mixture was stirred at room temperature undernitrogen atmosphere for 30 minutes. The mixture was then filtered toremove precipitated triethylamine hydrochloride. The filtrate was thenused without further purification in the preparation of CSP-10.

Bonding to silica to form CSP-10

The filtrate from the hydrosilation of CS-10, as described above,containing the crude ethoxysilane (Compound D, Table 8) was added to 5 gRegis Rexchrom silica (5 μ, 100 Å) which had been previously dried byazeotropic water removal with benzene. Dimethylformamide, (1 mL) wasthen added, and the slurry was carefully evaporated to dryness underreduced pressure. The moist slurry was then rocked in a Kugelrohr ovenat 90°-95° C./1 mm Hg for 24 hours. The silica gel was then washedextensively with ethanol and then methanol, slurried in methanol andpacked into a 4.6 mm×250 mm stainless steel HPLC column to affordCSP-10. Excess silica gel removed from the column packer reservoir wassubmitted for elemental analysis (C 7.27%; H 0.95%; N 0.71%) to reveal aloading of 0.18 mMole chiral selector per gram of stationary phase.After preliminary analysis, the residual silanols on the stationaryphase were endcapped by passing a solution of 2 mL ofhexamethyldisilazane (HMDS) in 50 mL dichloromethane through themethylene chloride equilibrated column at a flow rate of 1 mL/min.

Analytes and their separation

All chromatographic experiments were carried out at a nominal flow rateof 2.00 mL/min. Column void time was measured by injection oftri-t-butylbenzene, a presumed unretained solute. Variable temperaturedata were collected with the mobile phase reservoir and pump at ambienttemperature, and with the column immersed in a large constanttemperature bath. About two feet of 0.009 in ID stainless steel tubingwas used to connect the column to the injector and was wrapped aroundthe inverted column as a heat exchanger to thermally equilibrate themobile phase prior to column entry.

Mobile phases consisting of alkanes and lower molecular weight alcohols,and, optionally, containing lower molecular weight carboxylic acidsand/or lower molecular weight amines were used to permit separation ofenantiomers of naproxen and other analytes.

Enantiomeric mixtures of naproxen and selected α-arylacetic acidcompounds of interest were subjected to separation with HPLC columns tocompare the effectiveness of CS-10 of the present invention when formingthe active part of the stationary phase (CSP-10) in the column.

Two mobile phases were separately utilized: Mobile Phase A, whichcomprised 5% 2-propanol and 0.1% acetic acid in hexane, and Mobile PhaseB, which comprised 20% 2-propanol, 0.1% acetic acid and 0.1%triethylamine in hexane.

Chromatographic data for naproxen and nine other α-aryl acetic acidcompounds were obtained using the (R,R) configuration of CS-10 of theinvention. The results are presented below in Table 9.

                  TABLE 9                                                         ______________________________________                                        Separation of Underivatized naproxen                                          and other arylacetic acid compounds on CSP-10                                            Mobile Phase A                                                                            Mobile Phase B                                         Analyte      k'.sub.1                                                                             α    k'.sub.1                                                                            α                                  ______________________________________                                        naproxen     3.31   1.97       5.86  2.20                                     ibuprofen    0.27   1.22       0.75  1.20                                     ketoprofen   3.11   1.05       5.08  1.22                                     flurbiprofen 0.64   1.30       2.05  1.31                                     pirprofen    1.85   1.27       3.35  1.33                                     fenoprofen   0.57   1.40       1.46  1.43                                     cicloprofen  2.53   1.60       4.00  1.67                                     carprofen    2.20   1.40       6.30  1.42                                     tiaprofenic acid                                                                           6.40   >1.00      13.45 1.12                                     etodolac     0.87   1.23       --    --                                       ______________________________________                                         k'.sub.1 = the capacity factor for the first eluted enantiomer using the      indicated mobile phases and flow rates. The detector was operating at 254     nm.                                                                           α = the chromatographic separation factor                          

From these data, it can be seen that CSP-10 achieved a high degree ofchromatographic separation (α) of the underivatized analytes. UsingMobile Phase A, all of the analytes, except ketoprofen and tiaprofenicacid, were baseline resolved under these chromatographic conditions. Inmobile phases containing a small amount of triethylamine in addition toacetic acid (Mobile Phase B), baseline resolution of all the analyteswas easily obtained.

Chromatographic data for the amines, alcohol derivatives, epoxides andsulfoxides shown in Tables 2, 3, 4 and 5, respectively, were obtainedusing the (R,R) configuration of CS-10 of the invention using either ofMobile Phase A or Mobile Phase B, or a third Mobile Phase C, whichcomprised 2% 2-propanol in hexane; all other conditions were asdescribed above. The resolution results are shown in Tables 10, 11, 12,and 13, below.

                                      TABLE 10                                    __________________________________________________________________________    Separation of Amines on CSP-10                                                __________________________________________________________________________     ##STR45##                                                                     ##STR46##                                                                    __________________________________________________________________________

                  TABLE 11                                                        ______________________________________                                        Separation of Alcohol Derivatives on CSP-10                                   ______________________________________                                         ##STR47##                                                                    ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                        Separation of Epoxides on CSP-10                                              ______________________________________                                         ##STR48##                                                                    ______________________________________                                    

                  TABLE 13                                                        ______________________________________                                        Separation of Sulfoxides on CSP-10                                            ______________________________________                                         ##STR49##                                                                    ______________________________________                                    

As seen from these data, high degrees of resolution, as measured by thechromatographic separation factor, α, are obtained with the chiralselector of the present invention, as embodied on CSP-10.

EXAMPLE 2 Preparation of CS-2

The synthetic sequence used to prepare CS-2 is shown in Table 14, below.

                  TABLE 14                                                        ______________________________________                                         ##STR50##                                                                     ##STR51##                                                                     ##STR52##                                                                    ______________________________________                                    

Apparatus and Materials

Chromatographic analysis was performed using a Altex model 100A pump, aRheodyne model 7125 injector with a 20 μl sample loop, a Linear UVIS 200variable wavelength absorbance monitor, set at 254 nm, and aHewlett-Packard HP 2294A integrating recorder. All ¹ H NMR spectra wererecorded on a Varian XL 200 FT NMR spectrometer.

All reagents were of pharmaceutical or reagent grade and were usedwithout further purification. Solvents used were HPLC grade or distilledprior to use. Dimethylchlorosilane was obtained from Petrarch Systems,Bristol, Pa. Rexchrom 5 μ/100 Å silica gel was obtained from RegisChemical Co., Morton Grove, Ill.

Preparation of Racemic 4-oxo-3-allyl-1,2,3,4-tetrahydrophenanthrene(CS-2)

Transformation of the ketone, 4-oxo-1,2,3,4-tetrahydrophenanthrene(Compound E, Table 14), which ketone has been reported by Premasager, V.et al. in J. Org. Chem., 46, pp. 2974 (1981) to CS-2 followed the methodin Example 1 for CS-10.

Alkylation of the ketone (Compound E, Table 14) with allyl bromide gaveCompound F (Table 14). Reductive amination of Compound F (Table 14)followed by acylation with 3,5-dinitrobenzoyl chloride gave CS-2. ¹ HNMR (200 M Hz, CDCl₃) δ: 1.60 (m,1H), 2.10 (m,3H), 2.65 (m,1H), 3.19(m,2H), 5.12 (m,2H), 6.00 (m,1H), 6.18 (dd,1H, J=10 Hz and 3 Hz), 6.34(d,1H, J=10 Hz), 7.29 (d,1H), 7.45 (m,2H), 7.79 (m,2H), 8.05 (d,1H,J=8.4 Hz), 8.88 (d,2H, J=2.3 Hz).

Separation of the Enantiomers of CS-2

The enantiomers of CS-2 were chromatographically separated on a 25mm×900 mm column containing a chiral stationary phase derived from(S)-N-(1-naphthyl)leucine chiral stationary phase which was prepared asdescribed by Pirkle, Deming and Burke in Chirality, 3:183-187 (1991) thecontents of which are incorporated herein by reference.

Separation of the enantiomers of CS-2 was performed using this chiralstationary phase derived from (S)-N-(1-naphthyl)leucine at a flow rateof 40 ml/min. of 10% 2-propanol in hexane with continuous redistillationand recycling of mobile phase. Two bands were obtained. Samples of thenearly pure fast-eluting enantiomer of CS-2 having the (R,R)configuration were isolated, as were samples of the slow-elutingenantiomer of CS-2 having the (S,S) configuration (0.85 g).

Chiral Stationary Phase of CS-2

The synthetic sequence used to prepare to chiral stationary phase ofCS-2 is shown in Table 15, below.

                                      TABLE 15                                    __________________________________________________________________________     ##STR53##                                                                     ##STR54##                                                                    __________________________________________________________________________

Hydrosilation of CS-2

The second eluting enantiomer of CS-2 (0.85 g) assigned the (S,S)absolute configuration by a combination of HPLC, NMR, and x-raycrystallographic evidence was dissolved in a mixture of 10 mL ofdimethylchlorosilane and 10 mL of dichloromethane. Chloroplatinic acid(about 5 mg) dissolved in a minimum amount of 2-propanol was then addedand the reaction mixture was heated at reflux under a nitrogenatmosphere. After 1 h, a quenched aliquot of the reaction mixture showed(by TLC analysis) no remaining starting material. The reaction mixturewas evaporated to dryness on a rotary evaporator to give tile crudechlorosilane as a dark oil. Residual dimethylchlorosilane was removed bythree successive additions and evaporations of small portions ofdichloromethane. A mixture of 5 mL of triethylamine, 5 mL of absoluteethanol, and 5 mL of diethyl ether was then added to the crudechlorosilane and the mixture was stirred at room temperature under anitrogen atmosphere for 30 minutes. The mixture was filtered to removetriethylamine hydrochloride and evaporated to afford the crudeethoxyorganosilane which was purified by flash chromatography on silicausing 5% ethanol/dichloromethane as eluent to give 0.93 gethoxyorganosilane (Compound G, Table 15) (88% yield). ¹ H NMR (200M Hz,CDCl₃) δ: 0.09 (s,6H), 0.62 (m,2H), 1.18 (t,3H), 1.60 (m,5H), 2.05(m,2H), 3.10 (m,2H), 3.68 (q,2H), 6.11 (dd,1H), 6.33 (d,1H), 7.29(d,1H), 7.45 (m,2H), 7.79 (m,2H), 8.10 (d,1H), 8.85 (d,2 H), 9.10(t,1H).

Bonding to Silica to Form CSP-2

A solution of 0.93 g ethoxyorganosilane (Compound G, Table 15) dissolvedin 1 mL of dimethylformamide was added to a dichloromethane slurry of 5g of Regis Rexchorm silica (5 μ, 100 Å) which had been previously driedby azeotropic water removal with benzene. The slurry was carefullyevaporated to dryness under reduced pressure, then heated at 120° C./1torr for 24 h. The silica gel was washed extensively with ethanol andthen methanol, slurried in methanol and packed into a 4.6 mm×250 mmstainless steel HPLC column. Elemental analysis of residual packing (C4.95%; H 0.61%; N 0.56%) showed a loading of 2.0×10⁻⁴ moles of chiralselector per gram of stationary phase. The residual silanol groups wereendcapped by passing a solution of 2 mL of hexamethyldisilazane in 50 mLdichloromethane through the dichloromethane equilibrated column at aflow rate of 1 mL/min.

Analytes and their Separation

All chromatographic experiments were carried out at a nominal flow rateof 2.00 mL/min. unless otherwise indicated. Column void time wasmeasured by injection of tri-t-butylbenzene, a presumed unretainedsolute as reported by Pirkle, et al. in J. Liq. Chromatogr, 14, 1,(1991) incorporated herein by reference. ¹ H NMR chemical shifts werereported in ppm (δ) relative to tetramethylsilane. Variable temperaturedata were collected with the mobile phase reservoir and pump at ambienttemperature, and with the column immersed in a large constanttemperature bath. About two feet of 0.009 in ID stainless steel tubingwas used to connect the column to the injector and was wrapped aroundthe inverted column as a heat exchanger to thermally equilibrate themobile phase prior to column entry.

Enantiomeric mixtures of naproxen and selected α-arylacetic acidcompounds of interest were subjected to separation with HPLC columns tocompare the effectiveness of CS-2 of the present invention, when itforms the active part of the stationary phase of the column. Theseparation afforded by CS-2 under these circumstances was compared withCS-10 of the present invention as prepared according to Example 1; eachseparately formed the active part of the stationary phase (denoted asCSP-2 and CSP-10) in the respective columns.

The mobile phase utilized comprised 20% 2-propanol in hexane containing1 g/L ammonium acetate.

Chromatographic data for naproxen and seven other α-arylacetic acidcompounds were obtained using the S,S configurations of CS-2 and CS-10of the invention. The results are presented below in Table 16.

                  TABLE 16                                                        ______________________________________                                        Separation of Underivatized Naproxen and                                      Other Arylacetic Acid Compounds on CSP-10 and CSP-2                                    CSP-10       CSP-2                                                   Compound   k'.sub.1                                                                              k'.sub.2                                                                             α                                                                             k'.sub.1                                                                           k'.sub.2                                                                            α                            ______________________________________                                        Naproxen   3.96    8.95   2.26  1.71 5.01  2.93                               Ibuprofen  0.94    1.05   1.12  0.19 0.28  1.47                               Ketoprofen 4.53    5.03   1.11  1.39 1.79  1.29                               Flurbiprofen                                                                             1.63    1.94   1.19  0.37 0.59  1.59                               Pirprofen  2.53    3.49   1.38  0.85 1.54  1.81                               Fenaprofen 1.48    1.81   1.22  0.38 0.61  2.50                               Cicloprofen                                                                              3.03    5.18   1.71  1.16 2.50  2.15                               Tiaprofenic Acid                                                                         6.15    6.70   1.09  2.02 2.48  1.23                               ______________________________________                                         Conditions: Flow rate = 2.0 mL/min.; mobile phase = 20% 2propanol in          hexane containing 1 g/L ammonium acetate;                                     k'.sub.1 = capacity factor for first eluted enantiomer.                       k'.sub.2 = capacity factor for second eluted enantiomer.                      α = the chromatographic separation factor.                         

From these data, it can be seen that CSP-2 achieved an even higherdegree of chromatographic separation (α) of the underivatized analytesthan CSP-10, with an α for CSP-2 of nearly three (2.93, at roomtemperature) being obtained for naproxen. Analyte capacity factors(k's), as apparent in Table 16, were consistently less on theshort-tethered CSP-2 as opposed to the longer tethered CSP-10. This wasespecially true for the less retained enantiomer.

EXAMPLE 3 Preparation of CS-8 Apparatus and Materials

Melting points were taken on a Buchi apparatus and are uncorrected. ¹ HNMR spectra were recorded on a Varian XL-200 spectrometer in CDCl₃ andwere referenced to tetramethylsilane or residual CHCl₃ (7.24 ppm). IRspectra were taken on a IBM IR/32 FTIR spectrometer. High resolutionmass spectra were obtained on a Varian 731 mass spectrometer at SCS MassSpectrometry Laboratory, University of Illinois at Urbana-Champaign.

Chromatography was performed with a HPLC system which consists of anAnspec-Bischoff model 2200 HPLC pump, a Rheodyne 7125 injector with 20μl sample loop, a Milton Roy UV Monitor™ D fixed wavelength detectoroperating at 254 nm and a Kipp & Zonen BD 41 recorder.

Preparation of 3-(6,7-Dimethyl-1 and 2-naphthoyl)propanoic Acid

Anhydrous AlCl₃ (19 g, 0.14 mole) was added to 200 ml of CH₂ Cl₂ withstirring at 0° C. To the stirred heterogeneous solution was addedsuccinic anhydride (12 g, 0.12 mole) and then 2,3-dimethylnaphthalene(15.6 g, 0.1 mole) at 0° C. After stirring overnight at roomtemperature, 200 ml of 1N HCl, 10 ml of 12N HCL and then 300 ml ofethylacetate were added to the reaction mixture. The whole mixture wasshaken vigorously in a separatory funnel and then the two phases(organic phase:upper phase) were separated. The organic phase wasextracted with 1N NaOH. The NaOH solution was washed with ether (200 ml)and then acidified with 12N HCl to afford yellow solid material in theaqueous phase. The whole mixture was extracted with ethylacetate. Theethylacetate solution was dried over anhydrous Na₂ SO₄ and thenconcentrated to afford yellow solid material. This solid material wascrystallized from ethylacetate. The first crop (6.58 g, 25.7% yield) wasfound to be pure 3-(6,7,-dimethyl-2-naphthoyl)propanoic acid (6-isomer)and the second crop (6.85 g, 26.8% yield) was3-(6,7-dimethyl-1-naphthoyl)propanoic acid (α-isomer) by NMR.

β-Isomer: yellow needle crystal, mp 183.0°-185.0° C., ¹ H NMR (CDCl₃)δ2.45 (s,6H), 2.87 (t, J=6.7 Hz,2H), 3.45 (t, J=6.7 Hz,2H), 7.63 (s,1H),7.71 (s,1H), 7.77 (d, J=8.5 Hz,1H), 7.95 (d, J=8.5 Hz,1H), 8.41 (s,1H),IR (KBr) cm⁻¹ 3300-2800, 1698, 1678, 1610, 1597, Anal. calcd. for C₁₆H₁₆ O₃ : C, 74.98; H, 6.29. Found: C, 74.63; H, 6.17.

α-Isomer: yellowish solid, mp 162.0°-163.0° C., ¹ H NMR (CDCl₃) δ2.42(s,3H), 2.44 (S,3H), 2.89 (t, J=6.3 Hz, 2H), 3.40 (t, J=6.3 Hz,2H),7.37-7.44 (m,1H), 7.62 (s,1H), 7.87 (d, J=6.8 Hz,1H), 7.89 (d, J=8.3Hz,1H), 8.43 (s,1H), IR (KBr) cm⁻¹ 3330-2800, 1698, 1669, 1580, 1500,Anal. Calcd. for C₁₆ H₁₆ O₃ : C, 74.98; H, 6.29. Found: C, 75.22; H,6.18.

Preparation of 4-(6,7-Dimethyl-2-naphthyl)butanoic acid

The β-isomer, 3-(6,7-dimethyl-2-naphthoyl)propanoic acid (6.58 g, 0.026mole) was dissolved into 200 ml of THF in a hydrogenation pressurebottle. To the solution was carefully added 30% Pd/C (700 mg). The wholemixture was shaken for 15 hrs under H₂ (40 psi) at room temperature.After releasing pressure, Pd/C was removed by passing the THF solutionthrough the celite pad. The solution was concentrated to afford4-(6,7-Dimethyl-2-naphthyl)butanoic acid as a gray solid material (6 21g, 0.026 mole, 100% yield). mp 141.0°-142.0° C., ¹ H NMR (CDCl₃)δ1.98-2.12 (m,2H), 2.36-2.41 (m,8H), 2.81 (t, J=7.4 Hz,2H), 7.22 (d,J=8.3 Hz,1H), 7.49-7.55 (m,3H), 7.65 (d, J=8.3 Hz,1H), IR (KBr) cm⁻¹3700-3450, 2920, 1698, Anal. Calcd. for C₁₆ H₁₈ O₂ : C, 79.31; H, 7.49.Found: C, 79.28; H, 7.49.

Preparation of 6,7-Dimethyl-4-oxo-1,2,3,4-tetrahydrophenanthrene

4-(6,7-Dimethyl-2-naphthyl)butanoic acid (6.21 g, 0.026 mole) was addedto 40 ml of CH₃ SO₃ H. The mixture was heated to 90° C. until all solidmaterial disappeared (about 30 min.). The mixture was poured into iceand then extracted twice with ethylacetate. Combined ethylacetatesolution was dried over anhydrous Na₂ SO₄ and then concentrated. Afterflash chromatography on silica gel,6,7-Dimethyl-4-oxo-1,2,3,4-tetrahydrophenanthrene was obtained as a paleyellow solid material (4.96 g, 0.022 mole, 85% yield). mp 114.0°-115.0°C., ¹ H NMR (CDCl₃) δ2.12-2.20 (m,2H), 2.41 (s,3H), 2.47 (s,3H), 2.77(t, J=6.4 Hz,2H), 3.09 (t, J=6.4 Hz,2H), 7.21 (d, J=8.3 Hz,1H), 7.54(s,1H), 7.31 (d, J=8.3 Hz,1H), 9.20 (s,1 H), IR (KBr) cm⁻¹ 2930, 1669,1590, 1510, Anal. Calcd. for C₁₆ H₁₆ O: C, 85.6: H, 7.19. Found: C,86.00; H, 7.18.

Preparation of6,7-Dimethyl-4-oxo-3-(10-undecenyl)-1,2,3,4-tetrahydrophenanthrene

t-BuOK (3.6 g, 0.032 mole) was dissolved in 250 ml of dry benzene at40°-50° C. To the stirred solution was added6,7-Dimethyl-4-oxo-1,2,3,4-tetrahydrophenanthrene (3.6 g, 0.016 mole) in50 ml of dry benzene and then, 10-undecenyl iodide (4.58 g, 0.016 mole)at 30° C. under N₂. The mixture was heated to 60° C. for 2.5 hr underN₂. After cooling the reaction mixture to room temperature, water wasadded. The whole mixture was extracted twice with diethylether. Thecombined diethylether solution was dried over anhydrous MgSO₄ and thenconcentrated. Flash column chromatography of the residue on silica gelafforded6,7-Dimethyl-4-oxo-3-(10-undecenyl)-1,2,3,4-tetrahydrophenanthrene as asticky brown solid (2.36 g, 0.0063 mole, 39% yield) as a desiredproduct, and unreacted 6,7-Dimethyl-4-oxo-1,2,3,4-tetrahydrophenanthrene(1.70 g, 47% recovered). ¹ H NMR (CDCl₃) δ 1.29-1.62 (m,14H), 1.86-2.08(m,4H), 2.21-2.35 (m,2H), 2.40 (s,3H), 2.46 (s,3H), 2.52-2.63 (m,1H),3.07-3.13 (m,2H), 4.90-5.04 (m,2H), 5.75-5.89 (m,1H), 7.17 (d, J=8.2Hz,1H), 7.53 (s,1H), 7.77 (d, J=8.2 Hz,1H), 9.10 (s,1H), IR (KBr) cm⁻¹2920, 2850, 1669, 1600, exact (EI) mass. calcd. for C₂₇ H₃₆ O: 376.2766,Found: 376.2766.

Preparation of6,7-Dimethyl-4-[N-(3,5-dinitrobenzoyl)]amino-3-(10-undecenyl)-1,2,3,4-tetrahydrophenanthrene(CS-8)

6,7-Dimethyl-4-oxo-(10-undecenyl)-1,2,3,4-tetrahydrophenanthrene (6.6 g,0.018 mole) was dissolved in 300 ml of methyl alcohol in a pressurebottle. To the solution was added 60 g of ammonium acetate and 10 g ofsodiumcyanoborohydride. The whole mixture was heated to 100°-105° C. for48 hrs in the closed pressure bottle. After cooling down the reactionmixture to room temperature, the pressure bottle was opened carefully.After adding 200 ml of 1N HCl to the reaction mixture (which resulted inthe generation of HCN gas), methyl alcohol was removed from the reactionmixture using a rotary evaporator. The residual aqueous solution wasmade basic (pH>10) by adding KOtl pellets, and was then extracted twicewith diethyl ether. The organic phase was dried over anhydrous Na₂ SO₄and then concentrated to afford a viscous oily material. This viscousoily material was dissolved in 100 ml of dry CH₂ Cl₂. To the stirredsolution was added 3,5-dinitrobenzoyl chloride (5.52 g, 0.028 mole) andtriethylamine (4.2 ml, 0.030 mole). After stirring for 15 min. at roomtemperature, the reaction mixture was washed with 0.5N HCl, 0.5N NaOH,and then brine solution. The organic solution was dried over anhydrousNa₂ SO₄ and then concentrated. The residue was purified by flash columnchromatography on silica gel to afford a yellowish solid material (7.66g, 0.0134 mole, 76% yield). This solid-material was found to be themixture of cis and trans isomers of CS-8 (the ratio of cis:trans=4.9:1)by analysis on a chiral HPLC column.

Separation of the Enantiomers of CS-8

By chromatographing the mixture of cis and trans isomers of CS-8 on a(S)-N-(1-naphthyl)leucine chiral stationary phase packed into a MPLCcolumn, which chiral stationary phase is described by Pirkle, Deming andBurke in Chirality, 3:183-187 (1991) the contents of which areincorporated herein by reference, 2.68 g of enantiomerically pure cisCS-8, i.e.,(cis)-6,7-Dimethyl-4-[N-(3,5-dinitrobenzoyl)]amino-3-(10-undecenyl)-1,2,3,4-tetrahydrophenanthrene,(last eluted enantiomer) was obtained, as were samples of the trans formof CS-8 (the first eluted enantiomer). Physical data for cis CS-8,obtained as a yellowish solid, were as follows: mp 181°-182° C., ¹ H NMR(CDCl₃) δ1.19-1.39 (m,14H), 1.42-1.77 (m,3H), 1.96-2.07 (m,4H), 2.36(s,3H), 2.40 (s,3H), 3.03-3.10 (m,2H), 4.89-5.03 (m,2H), 5.74-5.88(m,1H), 6.08 (dd, J=9.2 Hz, J= 2.8 Hz,1H), 6.20 (d, J=9.2 Hz,1H), 7.16(d, J=8.2 Hz,1H), 7.52 (s,1H), 7.61 (d, J=8.2 Hz,1H), 7.85 (s,1H), 8.84(d, J=1.7 Hz,2H), 9.08 (t, J=1.7 Hz,1H), IR (KBr) CM⁻¹ 3440, 2920, 2850,1680, 1650, 1540, 1500, exact (EI) mass. calcd. for C₃₄ H₄₁ N₃ O₅ :571.3046, Found: 571.3046, [α]D²⁰ -126.2(c 091, CH₂ Cl₂).

Chiral Stationary Phase of (cis)-CS-8

Hydrosilation of (cis)-CS-8

Preparation of(Cis)-6,7-Dimethyl-4-[N-3,5-Dinitrobenzoyl)]amino-3-(10-dimethylethoxysilylundecyl)-1,2,3,4-tetrahydrophenanthrene

(Cis)-CS-8 (1.75 g, 3.06×10⁻³ mole) was dissolved in 20 ml of methylenechloride. To the solution were added 20 ml of dimethylchlorosilane and0.2 ml of a H₂ PtCl₆ solution (72 mg of H₂ PtCl₆ in 5 ml of isopropylalcohol). This mixture was refluxed under nitrogen with stirring. Afterrefluxing for 1.5 hr., excess dimethylchlorosilane and methylenechloride were removed by simple distillation followed by application ofhigh vacuum. The oily residue was dissolved in 30 ml of dry methylenechloride and then the mixture of ethyl alcohol and triethylamine (3 ml,1:1 mixture) was added. After stirring for 10 min. at room temperature,all solvent was removed and the residue was purified by flash columnchromatography on silica gel to afford(cis)-6,7-Dimethyl-4-[N-(3,5-Dinitrobenzoyl)]amino-3-(10-dimethylethoxysilylundecyl-1,2,3,4-tetrahydrophenanthreneas a yellowish dense liquid (0.7 g, 34% yield). ¹ H NMR (CDCl₃) δ0.09(s,6H), 0.54-0.62 (m,2H), 1.18 (t, J=7.0 Hz,3H), 1.22-1.44 (broad m,18H), 1.50-1.80 (m,3H), 1.95-2.13 (m,2H), 2.34 (s,3H), 2.40 (s,3H),3.05-3.08 (m,2H), 3.65 (q, J=7.0 Hz,2H), 6.09 (dd, J=9.2 Hz, J=3.2Hz,1H), 6.25 (d, J=9.2 Hz,1H), 7.13 (d, J=8.3 Hz,1H), 7.47 (s,1H), 7.56(d, J=8.3 Hz,1H), 7.85 (s,1H), 8.82 (d, J=2.2 Hz,2H), 9.00 (t, J=2.2Hz,1H), IR (KBr) cm⁻¹ 3350, 2910, 2850, 1630, 1550, 1510, exact (EI)mass. calcd, for C₃₈ H₅₃ N₃ O₆ Si: 675.3704 Found: 675.3706, [α]D²⁰-82.3 (c 1.00, CH₂ Cl₂).

Bonding to Silica to form CSP-8

A 200 ml flask equipped with a Dean-Stark trap and a condenser wascharged with 4.5 g of 5 μm Rexchrom silica gel and 60 ml of benzene.After heating at reflux until water was completely removed,enantiomerically pure(cis)-6,7-Dimethyl-4-[N-(3,5-Dinitrobenzoyl)]amino-3-(10-dimethylethoxysilylundecyl)-1,2,3,4-tetrahydrophenanthrene(700 mg) in 10 ml of dry benzene was added and heated to reflux again toremove water. After removal of water, 1 ml of dimethylformamide wasadded and then the solvent was carefully evaporated to dryness underreduced pressure. The whole mixture was heated to 100°-105° C. for 2hrs. in a Kugelrohr oven under vacuum. The silica gel was washedsequentially with benzene, methanol, ethylacetate, methylene chloride,hexane and pentane and then dried at 80° C. under vacuum. Anal. Found: C7 55%, H 0 93% N 0 55%, calcd. loading: 0.16 mmoles of chiral selectorper gram of stationary phase based on C. The modified silica gel wasslurried in methanol and packed into a 4.6 mm×250 mm stainless steelcolumn using a conventional method. The residual silanols were endcappedby eluting a solution of 2 ml of hexamethyldisilazane in 50 ml ofmethylene chloride through the CSP column previously charged withmethylene chloride.

Analytes and their Separation

All chromatographic experiments were carried out at a nominal flow rateof 2.00 mL/min. unless otherwise indicated. Column void time wasmeasured by injection of tri-t-butylbenzene, a presumed unretainedsolute, in the manner described by Pirkle, et al. in J. Liq.Chromatogr., 14, 1, (1991), incorporated herein by reference.

Mobile phases consisting of alkanes and lower molecular weight alcoholsand, optionally containing lower molecular weight carboxylic acidsand/or lower molecular weight amines were used to permit separation ofenantiomers of naproxen and other analytes.

Enantiomeric mixtures of naproxen and selected α-arylacetic acidcompound of interests and various analogues thereof were subjected toseparation with HPLC columns to compare the effectiveness of CS-8 of thepresent invention when forming the active part of the stationary phase(CSP-8) in the column. The chromatographic data was obtained using thecis configuration of CS-8 of the invention. The results are presentedbelow in Tables 17, 18, 19 and 20, which tables separately identify themobile phases utilized.

                                      TABLE 17                                    __________________________________________________________________________    Separation of underivatized naproxen and other                                2-arylpropionic acids and analogues thereof on CSP-8                                                        Mobile                                                                            Elution                                     2-Arylpropionic Acid                                                                              k.sub.1 '                                                                        k.sub.2 '                                                                         α                                                                          Phase                                                                             Order                                       __________________________________________________________________________    Naproxen            4.97                                                                             11.33                                                                             2.28                                                                             D   S                                           Ibuprofen           0.69                                                                             0.83                                                                              1.20                                                                             E                                               Flurbiprofen        1.47                                                                             2.07                                                                              1.41                                                                             E                                               Fenoprofen          1.00                                                                             1.89                                                                              1.89                                                                             E                                               Carprofen           8.17                                                                             10.33                                                                             1.31                                                                             D                                               Pirprofen           4.50                                                                             7.11                                                                              1.58                                                                             E                                               Cicloprofen         3.29                                                                             5.59                                                                              1.70                                                                             D                                               Tiaprofenic acid    4.29                                                                             4.71                                                                              1.10                                                                             D                                               Etodolac            3.33                                                                             4.46                                                                              1.34                                                                             E                                                ##STR55##          5.88                                                                             19.20                                                                             3.27                                                                             D                                                ##STR56##          4.33                                                                             12.60                                                                             2.91                                                                             D                                                ##STR57##          3.51                                                                             12.07                                                                             3.44                                                                             D                                                ##STR58##          2.20                                                                             2.33                                                                              1.06                                                                             D                                                ##STR59##          0.71                                                                             1.17                                                                              1.66                                                                             D                                               __________________________________________________________________________     Mobile Phase D was 0.1% acetic acid and 5% isopropyl alcohol in hexane.       Mobile Phase E was 0.1% acetic acid and 2% isopropyl alcohol in hexane.       Flow rate was 2 ml/min.                                                       k.sub.1 ' = The capacity factor for the first eluted enantiomer using the     indicated mobile phases and flow rates.                                       k.sub.2 ' = The capacity factor for the second eluted enantiomer using th     indicated mobile and flow rates.                                              α = The chromatographic separation factor.                         

From the date of Table 17, it can be seen that CSP-8 achieved a highdegree of chromatographic separation (α) of the underivatized analytes,especially naproxen.

Chromatographic data for the separation of underivatized naproxen andother arylacetic acid compounds using the cis-configuration of CSP-8 andMobile Phase F which comprises 20% isopropyl alcohol in hexanecontaining 1.00 ml acetic acid/L (0.1%) and 1 ml of triethylamine/L(0.1%), is shown in Table 18 below.

                  TABLE 18                                                        ______________________________________                                        Separation of Underivatized Naproxen and                                      Other Arylacetic Acids on CSP-8 using Mobile Phase F                          Solutes               k.sub.1 '                                                                            k.sub.2 '                                                                              α                                 ______________________________________                                        Naproxen              5.36   15.04    2.81                                    lbuprofen             0.43   0.60     1.40                                    Ketoprofen            3.00   4.26     1.42                                    Flurbiprofen          1.36   2.44     1.80                                    Fenoprofen            0.87   1.94     2.23                                    Carprofen             3.39   4.71     1.39                                    Pirprofen             2.73   5.26     1.93                                    Cicloprofen           4.00   8.39     2.10                                    Tiaprofenic acid      7.94   10.36    1.30                                    Etodolac              2.13   2.40     1.13                                     ##STR60##            4.47   14.59    3.26                                    ______________________________________                                         k.sub.1 ' = The capacity factor for the first eluted enantiomer using the     indicated mobile phase and flow rate.                                         k.sub.2 ' = The capacity factor for the second eluted enantiomer using th     indicated mobile phase and flow rate.                                         α = The chromatographic separation factor.                         

As can be seen from the data elucidated in Table 18 high levels ofchromatographic separation were obtained. Indeed, as compared to thatelucidated in Table 17 (using CSP-8 and Mobile Phases D and E), anincrease in chromatographic separation (α) for naproxen, ibuprofen andetodolac was obtained using CSP-8 in conjunction with Mobile Phase F.

Chromatographic data for the separation of enantiomers of3,5-Dinitrobenzamides of 1-(p-methoxyphenyl)alkylamines on CSP-8 (cisconfiguration) using Mobile Phase G which comprised 30% isopropylalcohol in hexane, is shown in Table 19, below. Flow rate was 20 ml/min.

                  TABLE 19                                                        ______________________________________                                        Separation of Enantiomers of 3,5-Dinitrobenzamides of                         1-(p-methoxyphenyl)alkylamines on CSP-8 using Mobile Phase G                   ##STR61##             k.sub.1 '                                                                             k.sub.2 '                                                                             α                                ______________________________________                                        R = CH.sub.3          15.07   36.26   2.41                                    R = CH.sub.2 CH.sub.3 10.99   24.86   2.26                                    R = (CH.sub.2).sub.2 CH.sub.3                                                                       11.69   24.41   2.09                                    R = (CH.sub.2).sub.3 CH.sub.3                                                                       11.01   24.86   2.26                                    R = (CH.sub.2).sub.4 CH.sub.3                                                                       10.71   23.29   2.17                                    R = (CH.sub.2).sub.5 CH.sub.3                                                                       10.20   22.86   2.24                                    R = (CH.sub.2).sub.6 CH.sub.3                                                                       9.84    22.57   2.29                                    R = (CH.sub.2).sub.7 CH.sub.3                                                                       9.40    22.03   2.34                                    R = (CH.sub.2).sub.8 CH.sub.3                                                                       8.90    21.50   2.42                                    R = (CH.sub.2).sub.9 CH.sub.3                                                                       7.57    18.69   2.47                                    R = (CH.sub.2).sub.10 CH.sub.3                                                                      7.30    18.43   2.52                                    R = (CH.sub.2 ).sub.12 CH.sub.3                                                                     6.93    18.41   2.66                                    R = (CH.sub.2).sub.14 CH.sub.3                                                                      6.29    17.40   2.77                                    R = (CH.sub.2).sub.16 CH.sub.3                                                                      5.64    16.29   2.89                                    ______________________________________                                         k.sub.1 ' = The capacity factor for the first eluted enantiomer using the     indicated mobile phase and flow rate.                                         k.sub.2 ' = The capacity factor for the second eluted enantiomer using th     indicated mobile phase and flow rate.                                         α = The chromatographic separation factor.                         

As seen from the data of Table 19, high levels of chromatographicseparation (α) was achieved for all the 3,5-dinitrobenzamides of1-(p-methoxyphenyl)alkylamines that were studied using CSP-8 and MobilePhase G.

Chromatographic data for the separation of a variety of other racemiccompounds on CSP-8 (cis configuration) are shown in Table 20 below. Themobile phases utilized for the experiments reported in Table 20comprised the percentage of isopropyl alcohol indicated in Table 20, inhexane. Flow rate was 2 ml/min.

                                      TABLE 20                                    __________________________________________________________________________    Separation of a Variety of Racemic                                            Compounds on CSP-8 using the Mobile Phase having                              the Percentage of Isopropyl Alcohol indicated in Hexane                                                        % isopropyl alcohol                          Solutes                k.sub.1 '                                                                        k.sub.2 '                                                                         α                                                                          in hexane                                    __________________________________________________________________________     ##STR62##             7.56                                                                             10.14                                                                             1.34                                                                             10%                                           ##STR63##             5.60                                                                             8.21                                                                              1.47                                                                             10%                                           ##STR64##             3.43                                                                             10.43                                                                             3.04                                                                              5%                                           ##STR65##             0.43                                                                             1.37                                                                              3.20                                                                             20%                                           ##STR66##             0.47                                                                             1.17                                                                              2.48                                                                             20%                                           ##STR67##             2.79                                                                             6.89                                                                              2.47                                                                             20%                                           ##STR68##             0.57                                                                             0.90                                                                              1.58                                                                             20%                                           ##STR69##             1.14                                                                             1.83                                                                              1.60                                                                             20%                                           ##STR70##             1.14                                                                             1.86                                                                              1.63                                                                             20%                                           ##STR71##             0.67                                                                             1.20                                                                              1.79                                                                             20%                                           ##STR72##             0.99                                                                             2.29                                                                              2.32                                                                             20%                                           ##STR73##             0.99                                                                             1.29                                                                              1.30                                                                             20%                                           ##STR74##             2.06                                                                             2.91                                                                              1.42                                                                             20%                                           ##STR75##             1.44                                                                             1.90                                                                              1.32                                                                             20%                                           ##STR76##             8.57                                                                             23.43                                                                             2.73                                                                             20%                                           ##STR77##             3.13                                                                             3.63                                                                              1.16                                                                             10%                                           ##STR78##             3.70                                                                             7.91                                                                              2.14                                                                             20%                                           ##STR79##             1.14                                                                             2.00                                                                              1.75                                                                             10%                                          __________________________________________________________________________     k.sub.1 ' = The capacity factor for the first eluted enantiomer using the     indicated mobile phase and flow rate.                                         k.sub.2 ' = The capacity factor for the second eluted enantiomer using th     indicated mobile phase and flow rate.                                         α = The chromatographic separation factor.                         

As apparent from Table 20, CS-8 of the present invention, forming theactive portion of chiral stationary phase CSP-8, showed high degrees ofchromatographic separation (α) over a wide range of different racemates.

What is claimed is:
 1. A chiral selector useful as a chiral stationaryphase having the formula: ##STR80## wherein R₁ is ##STR81## R₂ is O, Sor NH; R₃ and R₄ are each independently hydrogen or lower alkyl;R₅ ishydrogen or CH═CH₂ ; R₆ and R₇ are each independently hydrogen, loweralkyl or R₆ and R₇ are attached to form a 6 member aromatic ring; X isO, S, NH or CH; X₁ is O, S, NH or CH; m is 0 or 1; n is 0 or 1; and R₈and R₉ are each independently NO₂, N(R₁₀)₃ ⁺, CN, COOR₁₁, SO₃ H orCOR₁₂, wherein R₁₀, R₁₁ and R₁₂ are each independently hydrogen or loweralkyl; and o is 0 or an integer from 1 to 12, said compound being an Ror an S enantiomer or a mixture of R and S enantiomers.
 2. The chiralselector of claim 1 wherein R₁ is ##STR82## and R₂ is NH.
 3. The chiralselector of claim 2 whereinR₃ and R₄ are each independently hydrogen ormethyl; R₁₀, R₁₁ and R₁₂ are each independently hydrogen or methyl; ando is an integer from 6 to
 10. 4. The chiral selector of claim 3whereinR₃ and R₄ are each hydrogen; R₅ is CH═CH₂ ; R₈ and R₉ are eachNO₂ ; and o is
 8. 5. The chiral selector of claim 4 whereinR₆ and R₇ areattached to form a 6 member aromatic ring; X is O; m is 1; and n is 0.6. The chiral selector of claim 4 whereinR₆ and R₇ are attached to forma 6 member aromatic ring; X₁ is O; m is 0; and n is
 1. 7. The chiralselector of claim 4 whereinR₆ and R₇ are each independently methyl; Xand X₁ are each CH; and m and n are each
 1. 8. The chiral selector ofclaim 4 whereinR₆ and R₇ are each hydrogen; X and X₁ are each CH; and mand n are each
 1. 9. The chiral selector of claim 2 whereinR₃ and R₄ areeach independently hydrogen or methyl; R₁₀, R₁₁ and R₁₂ are eachindependently hydrogen or methyl; and o is 0 or an integer from 1 to 5.10. The chiral selector of claim 9 whereinR₃ and R₄ are each hydrogen;R₅ is CH═CH₂ ; R₈ and R₉ are each NO₂ ; and o is 0 or 1 or
 2. 11. Thechiral selector of claim 10 whereinR₆ and R₇ are each hydrogen; X and X₁are each CH; m and n are each 1; and o is 0.